Dispersions and process therefor



Patented Apr. 11, 1967 3,313,641 DISPERSHONS AND PRGCESS THEREFGR Peter .iochen Boa-chart, Eiirhart, Ind, assignor to Mites Laboratories, Ind, Eiiahart, Ind, a corporation of Indiana No Drawing. Filed Nov. 18, 1963, Se". No. 324,203 7 Claims. (Ci. 106-213) This invention relates to a process for producing a stable dispersion of dialdehyde polysaccharides in water. More particularly, it relates to the process of reacting hydrogen peroxides with a water slurry of dialdehyde polysaccharides and to the novel stable dispersions prepared thereby.

Dialdehyde polysaccharides, such as dialdehyde corn starch, are well known in the art and are known to be useful for increasing the wet strength of paper, for example. However, the water solubility and water dispersibility of dialdehyde polysaccharides are quite low and complicated procedures are necessary in order to get suficient dialdehyde polysaccharide into dispersion so that the paper or paper pulp can be treated with it. This is especially true when the dispersions are to be prepared in high concentrations containing as much as 2030 weight percent solids. Prior art dispersions of dialdehyde polysaccharides were limited in utility since they became unstable as the polymer chain began to degrade when stored a week or longer at room temperature.

It is an object of the present invention to provide a process for preparing high solids content dispersions of dialdehyde polysaccharides in water.

It is another object of the present invention to provide water dispersions of dialdehyde polysaccharides that have high solids content and have improved resistance to degradation upon standing over a prolonged period of time.

According to the present invention, a dialdehyde polysaccharide-water slurry containing up to about 30 weight percent dialdehyde polysaccharide and substantially free of metal ions is reacted with from about 0.5 to 2.0 weight percent hydrogen peroxide (based on weight of dialdehyde polysaccharide) at a reaction temperature of from about 75 C. to about 95 C. Preferably the hydrogen peroxide is employed in amounts from about 1 to about 2 weight percent, based on weight of dialdehyde polysaccharide. The reaction is continued for a period of from about 30 to 60 minutes and then the resulting dispersion is cooled to room temperature. This stable dispersion containing from about 10 to about 30 weight percent dialdehyde polysaccharide can be used immediately or it can be stored at room temperature for several months without change in appearance, viscosity or loss in efiectiveness as a wet strength agent for paper. The hydrogen peroxide oxidizes some of the aldehyde groups of the dialdehyde polysaccharide to carboxy groups. This improves thedispersibility. The dispersion thus contains a carboxylated dialdehydepolysaccharide.

The dialdehyde polysaccharides useful as starting materials in the present process of preparing stable dispersions are frequently referred so as periodate oxidized polysaccharides. This is due to their preparation by the wellknown oxidation of polysaccharides with periodic acid. This preparation can 'be illustrated by the conversion of starch to dialdehyde starch or periodate oxodized starch using periodic acid in accordance with the following equation:

CHzOH onion n H l /H I t?T H ll 0 O H103 H2O wherein It stands for the number of repeating structural units in the molecule, which may range from as few as about 20 to as many as several thousand. The preparation of dialdehyde starch is more particularly described in US. Patents 2,648,629 of W. Dvonch et al. and 2,713,- 553 of C. L. Mehltretter.

The dialdehyde polysaccharides useful in preparing dispersions of the present invention may be the dialdehyde derivative of any polysaccharide, such as corn, wheat, rice, tapioca or potato starches, amyloses, amylopectins, celluloses, gums, dextrans, algins, inulins and the like. Of these polysaccharides, the dialdehyde derivatives known generically as dialdehyde starch are the best known and most widely used. However, where it is desired to have dispersions of dialdehyde derivatives of other polysaccharides, these may be used as well. The dialdehyde polysaccharides useful in the present invention can contain from about 0.5 to about 100 mole percent dialdehyde saccharide units. In general, it is preferred to use dialdehyde polysaccharides which are about 90 percent to 100 percent oxidized; i.e., those wherein about 90 to 100 of each 100 of the original anhydroglucose units have been converted to dialdehyde units such as by periodate oxidation as above described.

The water used in the preparation of the stable dis persions of the present invention should be substantially free of metal ions. Such ions can cause hydrolysis and degradation of the dialdehyde polysaccharides. Distilled water or deionized water can be used in the present invention.

The hydrogen peroxide useful in the present invention is used in the form of commercially available aqueous solutions containing, for example, from about 30 to about weight percent hydrogen peroxide.

The overall temperature range useful in the preparation of stable water dispersions of dialdehyde polysaccharides is from about C. to about C. Within this range, the particular temperature is generally dependent upon the dialdehyde polysaccharide concentration in the slurry and the concentration of the hydrogen peroxide supplied for oxidation of some of the aldehyde groups of the dialdehyde poiysaccharide. Higher temperatures are required as the dialdehyde polysaccharide concentration in the slurry increases. There is thus a substantially direct relationship between dialdehyde polysaccharide concentration and reaction temperature. On the other hand, the temperature required tends to decrease as the hydrogen peroxide concentration increases. There is thus a substantially inverse relationship between hydrogen peroxide concentration and reaction temperature.

In carrying out the process of the present invention, the dialdehyde polysaccharide, in the presence of hydrogen peroxide, reaches a stage of maximum swelling of the dialdehyde polysaccharide granules at 7595 C. Within about 5-15 minutes. With moderate stirring at this temperature a gradual rupture of the swollen granules occurs and homogeneous dispersions are formed within a period of from about 30 to about 60 minutes of total heating time, depending on temperature, concentration of dialdehyde polysaccharide and total amount hydrogen peroxide used.

The novel dispersions of the present invention comprise the reaction product of a substantially metal ionfree water slurry of dialdehyde polysaccharide and hydrogen peroxide wherein such reaction was carried out at about 75-95 C. for about 30-60 minutes. These dispersions are quite stable and can be used in a well-known known manner employing 21 Noble and Wood Handsheet Machine. These sheets were dried for 2 minutes at 200 F. (933 (3.). Similar handsheets were prepared from the same paper pulp slurry but which had not been treated manner to impart wet strength improvements to paper. 5 with the cationic dispersion. The treated and untreated When the novel dispersions of the present invention are handsheets were soaked in room temperature d1st1lled used for paper treatment they are preferably used in water for 5 minutes and the tensile strengths were meascombination with a cationizing agent or retention aid ured by standard techniques. The handsheets prepared to assist in coupling the dialdehyde polysaccharide to the from pulp that had been treated with the novel dialdehyde paper fibers. These cationizing agents or retention aids polysaccharide dispersion of the present invention had an are the well-known cationic starches, polymeric amines average wet tensile strength of 7.4 lbs/1n. of Width. and polyamides. The cationizing agent can be added first Paper prepared from untreated pulp had average wet to a slurry of paper pulp followed by addition of the tensile strength of only 1.6 lbs./in. of width. After a dialdehyde polysaccharide dispersion or the cationizing storage time of 3 months, an aliquot part of the Example agent and the dialdehyde polysaccharide dispersion can be 1 dispersion was eaiiOIliZed With Zirconium oxyehlofide mixed together and this mixture applied to the paper and added to paper pulp in the same manner as described pulp lurry, Water soluble compounds of ir onium, above using same concentrations of dispersion, cationsuch as Zirconium oxychloride, can also be used as cationizing agent and pulp. Handsheets prepared from this izing agents. treated pulp had average wet tensile strength of 7.0 lbs./ The following examples serve to illustrate, but not to in. of width. This clearly shows the improved stability limit, the practice of th inve tio over prolonged storage periods of the novel dispersions Example 1 of the present invention prepared by a novel process. To an open beaker, equipped with stirrer and ther- Example 3 mometer, and placed in a steam bath, were charged 500 2; Various dlspersions of dialdehyde polysaccharides in m1. of distilled water and 150 g. of dialdehyde corn starch Substantially metal ion-free Water were P P pl wherein 96 percent of the anhydroglucose units of the ing different concentrations of dialdehyde polysaccharides corn starch were oxidized to dialdehyde saccharide units. and different amounts of hydrogen PeYOXIde- The The mixture was stirred until the dialdehyde starch was efal Preparation Procedure the Same as described in completely wetted, and then the resulting slurry was ElfiamPle 1 above- These fhSPeISIOIIS Were h n mixed heated to 90-92 C. Six (6) grams of 50'weight percent h 20 Weight P P llfeehiufh oXyehlorlde 30 aqueous hydrogen peroxide were added (2 weight percent Welghh Percent Of a y l r a hyd C011- hydrogen peroxide based on weight of dialdehyde starch) dehsatlefi Product based 011 f y Weight of the dlaldehyde and the reaction mixture Was maintained at 90-92 C. polysaeeharide, and the catloniled dispersions w mwith moderate stirring for a total of 30 minutes. After P y to Prepare handsheets- The Wet teIlSlle Strengths 10 minutes of heating the slurry formed a thick paste. these hendsheets e measured y Well-known e With continued heating the paste viscosity diminished and l Each of the p e was tested f effectivea translucent dispersion was formed after about 30 min- Hess as 3 Wet Strength agent P l? after 24 hours and Utes of heating. The resulting dispersion was coded to after 4 weeks. Two of the dispersions were also allowed room temperature and Stored in a glass jar at room term to stand for 22 weeks. The dialdehyde polysaccharide peramre f three months During this storage period used as raw material was the same as described in Exthere were no signs of instability, polymer degradation or ample For companson Purposes, the e tenslle viscosity change strengths were measured for handsheets employing as the Example 2 wet strength agents prior art dispersions of dialdehyde polysaccharides in water. These prior art dispersions em- The dlspefsloh Prepared 1h Example 1 ebove was tested ployed, respectively, 5 and 10 weight percent solids and as a wet strength agent for paper lmmediately after f were prepared in water having total alkalinity of 100 matron and after the three month s torage period. An ppm. and 200 ppm respectively The total a1ka aliquot part of the dispersion was m xed with 20 welght linity of water is well-known to be expressed in terms P zlreonl'llm oxychlorlde Catlohlzlhg agent besed Q of parts per million of equivalent calcium carbonate. y h' .welght of e dlfildehyde Starch centalned In Alkalinity is measured by the procedure set forth in the dispersion. After diluting the mixture with distilled TAPPI Standards and suggested Methods T 620M55, water to a concentration of 1 weight percent solids, the page 4, cationic dispersion was added to a bleached kraft pulp The results are shown in the following table.

Heating conditions Wet tensile strength, lbs/in. width, 40 lb. basis weights Dispers1on,we1ght Weight perpercent solids cent, H202 employed Temp., C. Time, min. Within Zl Atter After 22 hrs. weeks weeks Prior art 5 -90 35 7. 9 8. 0 Prior art 10 -92 45 5. 4 3. 1

1 Zirconium oxychloride cationizer. 2 Dicyandiamidermaldehyde condensation product as cationizer.

slurry having a Canadian Standard Freeness of 450 cc. The cationic dispersion was used in an amount of 1 weight percent dialdehyde starch based on dry weight of the pulp. After a mixing and contacting time of 1-3 minutes, the pulp mixture was used to make handsheets in a well- It can be seen from the above table that the novel dispersions of the present invention provide high wet tensile strengths at high solids levels and such etfectiveness is retained over relatively long periods of time. The prior art dispersions on the other hand are limited to relatively lower solids content and the effectiveness after storage is substantially reduced.

What is claimed is:

1. A process for preparing stable dispersions of dialdehyde polysaccharides in Water which comprises forming a slurry of dialdehyde polysaccharide in substantially metal ion-free water, said slurry containing up to about 30 Weight percent solids, contacting said slurry with from about 0.5 to about 2.0 weight percent hydrogen peroxide based on weight of dialdehyde polysaccharide, said contact taking place at a reaction temperature of from about 75 C. to about 95 C. for a period of from about 30 to about 60 minutes, and then cooling the resulting dispersion to room temperature.

2. A process for preparing stable dispersions of dialdehyde polysaccharides in water which comprises forming a slurry of dialdehyde polysaccharide in substantially metal ion-free Water, said slurry containing from about to about 30 Weight percent solids, contacting said slurry with from about 1 to about 2 Weight percent hydrogen peroxide based on Weight of dialdehyde polysaccharide, said contact taking place at a reaction temperature of from about 75 C. to about 95 C. for a period of from about 30 to about 60 minutes, and then cooling the resulting dispersion to room temperature.

3. A process as claimed in claim 1 wherein the dialdehyde polysaccharide contains from about 0.5 to about 100 mole percent dialdehyde saccharide units.

4. A process as claimed in claim 1 wherein the dialdehyde polysaccharide contains from about 90 to about 100 mole percent dialdehyde saccharide units.

5. A process as claimed in claim 2 wherein the dialdehyde polysaccharide contains from about 0.5 to about 100 mole percent dialdehyde saccharide units.

6. A process as claimed in claim 2 wherein the dialdehyde polysaccharide contains from about 90 to about 100 mole percent dialdehyde saccharide units.

7. A stable dispersion of carboxylated dialdehyde polysaccharide in Water which comprises the room temperature cooled product resulting from the reaction of a substantially metal ion-free water slurry of dialdehyde polysaccharide containing up to Weight percent solids with from about 0.5 to about 2.0 weight percent hydrogen peroxide based on weight of dialdehyde polysaccharide, wherein such reaction was carried out at about 95 C. for about 30-60 minutes.

References Cited by the Examiner UNITED STATES PATENTS 2,669,523 2/1954 Kerr et al 1062l3 2,894,945 7/1959 Hofreiter et al. 3,081,199 3/1963 Taylor 106-213 ALEXANDER H. BRODMERKEL, Primary Examiner. L. B. HAYES, Assistant Examiner. 

1. A PROCESS FOR PREPARING STABLE DISPERSION OF DIALDEHYDE POLYSACCHARIDES IN WATER WHICH COMPRISES FORMING A SLURRY OF DIALDEHYDE POLYSACCHARIDE IN SUBSTANTIALLY METAL ION-FREE WATER, SAID SLURRY CONTAINING UP TO ABOUT 30 WEIGHT PERCENT SOLIDS, CONTACTING SAID SLURRY WITH FROM ABOUT 0.5 TO ABOUT 2.0 WEIGHT PERCENT HYDROGEN PEROXIDE BASED ON WEIGHT OF DIALDEHYDE POLYSACCHARIDE, SAID CONTACT TAKING PLACE AT A REACTION TEMPERATURE OF FROM ABOUT 75*C. TO ABOUT 95*C. FOR A PERIOD OF FROM ABOUT 30 TO ABOUT 60 MINUTES, AND THEN COOLING THE RESULTING DISPERSION TO ROOM TEMPERATURE. 